The effect of hyperbaric oxygen therapy in head and neck cancer patients with radiation induced dysphagia-a systematic review.

PURPOSE: The aim of this systematic review was to assess the role of hyperbaric oxygen therapy  (HBOT) in patients with dysphagia after radiation therapy for head and neck cancer. METHOD: A systematic search was conducted in the electronic databases Ovid MEDLINE, Ovid Embase, and Cochrane Central Register of Controlled Trials for relevant studies until March 14, 2023. No restriction on language or publication date. The criteria for inclusion: patients with HNC who had received both radiation therapy and HBOT as 1) a preventive treatment against swallowing difficulties, 2) to preserve swallowing function, or 3) to promote swallowing difficulties. RESULTS: We identified 1396 records. After removal of 31 duplicates, 1365 records were accessible for title and abstract screening. This yielded 53 studies for full text assessment. Six studies met the eligibility criteria and were included for qualitative analysis. CONCLUSION: Evidence of HBOT benefits in patients with dysphagia after radiation therapy for head and neck cancer is inconsistent. Well-designed studies using validated outcome measures and long-term follow-up are warranted.

High-dose loco-regional pattern of failure after primary radiotherapy in p16 positive and negative head and neck squamous cell carcinoma - A DAHANCA 19 study.

Introduction: Patients with failure after primary radiotherapy (RT) for head and neck squamous cell carcinoma (HNSCC) have a poor prognosis. This study investigates pattern of failure after primary curatively intended IMRT in a randomized controlled trial in relation to HPV/p16 status. Material and methods: Patients with HNSCC of the oral cavity, oropharynx (OPSCC), hypopharynx or larynx were treated with primary curative IMRT (+/-cisplatin) and concomitant nimorazole between 2007 and 12. Of 608 patients, 151 had loco-regional failure within five years, from whom 130 pairs of scans (planning-CT and diagnostic failure scan) were collected and deformably co-registered. Point of origin-based pattern of failure analysis was conducted, including distance to CTV1 and GTV, and estimated dose coverage of the point of origin. Results: Of 130 patients with pairs of scans, 104 (80 %) had at least one local or regional failure site covered by 95 % of prescribed dose and 87 (67 %) of the failures had point of origin within the high-dose CTV (CTV1). Of failures from primary p16 + OPSCC, the majority of both mucosal (84 %) and nodal (61 %) failures were covered by curative doses. For p16- tumors (oral cavity, OPSCC p16neg, hypopharynx and larynx), 75 % of mucosal and 66 % of nodal failures were high-dose failures. Conclusion: Radioresistance is the primary cause of failure after RT for HNSCC irrespective of HPV/p16 status. Thus, focus on predictors for the response to RT is warranted to identify patients with higher risk of high-dose failure that might benefit from intensified treatment regimens.

Comparison of 3-year local control using DAHANCA radiotherapy guidelines before and after implementation of five millimetres geometrical GTV to high-dose CTV margin.

INTRODUCTION: Treatment planning using a five-millimetre geometrical margin from GTV to high-dose CTV (CTV1) has been used in DAHANCA treatment centres since 2013. We aimed to evaluate changes in CTV1 volumes, local control (LC), and recurrence pattern after the implementation of five-millimetre geometrical margins nationally. MATERIALS AND METHODS: 1,948 patients with pharyngeal, and laryngeal squamous cell carcinomas completed definitive IMRT-based treatment in 2010-2012 and 2013-2015 in three centres. The patient-specific margin was calculated as median surface distance from primary tumour GTV (GTV-T) to CTV1. Radiologically verified local recurrences were analysed using a centre of mass (COM) of the delineated recurrence volume, measuring the shortest distance between COM to GTV-T and CTV1 boundaries. RESULTS: Median GTV-CTV1 was 0.9 (0.0-0.97) and 0.47 cm (0.4-0.5) for 2010-2012 and 2013-2015, respectively. Median CTV1 changed in three centres from 76, 28, 42 cm3 to 61, 53, 62 cm3 for 2010-2012 and 2013-2015, respectively. Local failures occurred at 247 patients during first three years after radiotherapy. The 3-year LC rate for 2010-2012 and 2013-2015 was 0.84 and 0.87 (p = 0.06). Out of 146 radiology-verified analysable local recurrences, 102 (69.9%) were inside the CTV1. In 74.6% and 91% of cases, the LRs were covered by 95% isodose in 2010-2012 and 2013-2015, respectively. CONCLUSION: DAHANCA radiotherapy guidelines based on a geometrically generated isotropic CTV1 margin led to less variation in treatment volumes and between centres than previous guidelines. The transition towards consensus GTV-CTV1 margins did not influence local tumour control. The majority of local recurrences were inside CTV1 and covered by the prescription dose.

Tumor volume and cancer stem cell expression as prognostic markers for high-dose loco-regional failure in head and neck squamous cell carcinoma - A DAHANCA 19 study.

BACKGROUND AND PURPOSE: Reliable and accessible biomarkers for patients with Head and Neck Squamous Cell Carcinoma (HNSCC) are warranted for biologically driven radiotherapy (RT). This study aimed to investigate the prognostic value of putative cancer stem cell (CSC) markers, hypoxia, and tumor volume using loco-regional high-dose failure (HDF) as endpoint. MATERIALS AND METHODS: Tumor tissue was retrieved from patients treated with primary chemo-(C-)RT and nimorazole for HNSCC in the Danish Head and Neck Cancer Study Group (DAHANCA) 19 study. Tumor volume, hypoxic classification, and expression of CSC markers CD44, SLC3A2, and MET were analyzed. For patients with eligible data on all parameters (n = 340), the risk of HDF following primary chemo-(C-)RT were analyzed by these biomarkers as a whole and stratified for p16-positive oropharynx (p16 + OPSCC) vs p16-negative (p16-) tumors (oral cavity, p16- oropharynx, hypopharynx and larynx). RESULTS: Higher risk of HDF was seen for patients with larger primary and nodal volume (>25 cm3, Hazard Ratio (HR): 3.00 [95 % CI: 1.73-5.18]), high SLC3A2 (HR: 2.99 [1.28-6.99]), CD44 (>30 % positive, HR: 2.29 [1.05-5.00]), and p16- tumors (HR: 2.53 [1.05-6.11]). p16- tumors had a higher CSC marker expression than p16 + OPSCC. The factors associated with the highest risk of HDF were larger volume (HR: 3.29 [1.79-6.04]) for p16- tumors (n = 178) and high SLC3A2 (HR: 6.19 [1.58-24.23]) for p16 + OPSCC (n = 162). CONCLUSION: Tumor volume, p16, and CSC markers are potential biomarkers for HDF for patients with HNSCC treated with (C-)RT. Lower expression of CSC in p16 + OPSCC may contribute to better tumor control.

Evaluation of decentralised model-based selection of head and neck cancer patients for a proton treatment study. DAHANCA 35.

INTRODUCTION: Proton treatment can potentially spare patients with H&N cancer for substantial treatment-related toxicities. The current study investigated the reproducibility of a decentralised model-based selection of patients for a proton treatment study when the selection plans were compared to the clinical treatment plans performed at the proton centre. METHODS: Sixty-three patients were selected for proton treatment in the six Danish Head and Neck Cancer (DAHANCA) centres. The patients were selected based on normal tissue complication probability (NTCP) estimated from local photon and proton treatment plans, which showed a ΔNTCP greater than 5%-point for either grade 2 + dysphagia or grade 2 + xerostomia at six months. The selection plans were compared to the clinical treatment plans performed at the proton centre. RESULTS: Of the 63 patients, 49 and 25 were selected based on an estimated benefit in risk of dysphagia and xerostomia, respectively. Eleven patients had a potential gain in both toxicities. The mean ΔNTCP changed from the local selection plan comparison to the clinical comparison from 6.9 to 5.3 %-points (p = 0.01) and 7.3 to 4.9 %-points (p = 0.03) for dysphagia and xerostomia, respectively. Volume differences in both CTV and OAR could add to the loss in ΔNTCP. 61 of the 63 clinical plans had a positive ΔNTCP, and 38 had a ΔNTCP of 5%-points for at least one of the two endpoints. CONCLUSION: A local treatment plan comparison can be used to select candidates for proton treatment. The local comparative proton plan overestimates the potential benefit of the clinical proton plan. Continuous quality assurance of the delineation procedures and planning is crucial in the subsequent randomised clinical trial setting.

HPV testing versus p16 immunohistochemistry in oropharyngeal squamous cell carcinoma: results from the DAHANCA 19 study.

INTRODUCTION: The prognosis after primary (chemo-)radiotherapy for oropharyngeal squamous cell carcinoma (OPSCC) is affected by Human Papillomavirus (HPV) status, with a better prognosis in HPV-positive OPSCC. HPV-status is routinely assessed by p16 immunohistochemistry (IHC), but additional HPV DNA testing is debated. Also, there are numerous HPV genotypes, which prognostic role may need clarification. The purpose of this study was: (1) to test a custom-made targeted HPV next generation sequencing (NGS) panel in OPSCC, (2) to determine correlation with p16 IHC, and (3) to assess the impact of HPV DNA testing on outcome in the prospectively randomized clinical trial DAHANCA 19. MATERIALS AND METHODS: We included 271 patients with OPSCC treated with primary (chemo-)radiotherapy in the DAHANCA 19 trial. Of these, 199 (73%) were p16-positive. HPV-status was determined by targeted HPV next generation sequencing (NGS), using a custom-made HPV genotyping panel. RESULTS: HPV was detected in 194 tumor samples. p16 IHC and NGS HPV status were concordant in 265 (98%) of 271 patients, whereas we did not detect HPV DNA in 5 p16-positive tumors. HPV16 accounted for 169 of 194 HPV-positive cases (87%). HPV genotypes 18, 31, 33, 35, and 59 were also detected.Loco-regional failure and overall survival were similar whether patients were separated by p16 IHC, or HPV DNA status (p < 0.0001 for all) and did not depend on HPV genotype (p = 0.9 and p = 0.7). CONCLUSION: In the present study, HPV DNA testing or typing in a Danish OPSCC cohort did not add additional information to p16 IHC, the most widely used and accepted prognostic indicator.

A national repository of complete radiotherapy plans: design, Results, and experiences.

BACKGROUND: Previously, many radiotherapy (RT) trials were based on a few selected dose measures. Many research questions, however, rely on access to the complete dose information. To support such access, a national RT plan database was created. The system focuses on data security, ease of use, and re-use of data. This article reports on the development and structure, and the functionality and experience of this national database. METHODS AND MATERIALS: A system based on the DICOM-RT standard, DcmCollab, was implemented with direct connections to all Danish RT centres. Data is segregated into any number of collaboration projects. User access to the system is provided through a web interface. The database has a finely defined access permission model to support legal requirements. RESULTS: Currently, data for more than 14,000 patients have been submitted to the system, and more than 50 research projects are registered. The system is used for data collection, trial quality assurance, and audit data set generation.Users reported that the process of submitting data, waiting for it to be processed, and then manually attaching it to a project was resource intensive. This was accommodated with the introduction of triggering features, eliminating much of the need for users to manage data manually. Many other features, including structure name mapping, RT plan viewer, and the Audit Tool were developed based on user input. CONCLUSION: The DcmCollab system has provided an efficient means to collect and access complete datasets for multi-centre RT research. This stands in contrast with previous methods of collecting RT data in multi-centre settings, where only singular data points were manually reported. To accommodate the evolving legal environment, DcmCollab has been defined as a 'data processor', meaning that it is a tool for other research projects to use rather than a research project in and of itself.

Socioeconomic position and the pre-diagnostic interval among patients diagnosed with head and neck squamous cell carcinoma - a population-based study from DAHANCA.

BACKGROUND: The socioeconomic differences in survival are pronounced for patients diagnosed with head and neck cancer; disease stage at diagnosis is suggested to be a main driver of this association. This nationwide, population-based study investigates socioeconomic differences in the pre-diagnostic interval and disease stage at diagnosis. MATERIAL AND METHODS: Information on patient-reported symptoms, symptom onset and disease-specific factors was obtained from the nationwide population-based Danish Head and Neck Cancer Group (DAHANCA) database for patients diagnosed with head and neck squamous cell carcinoma between 2008 and 2019 in Denmark. Socioeconomic position (SEP) was measured by individual-level education, income and cohabitation status obtained from administrative registers. Socioeconomic differences in the interval from symptom onset to diagnosis were investigated in general linear models with 95% confidence intervals (CIs); overall and by subsite, symptom and comorbidity score. Consultation patterns prior to diagnosis were examined using methods for change-point detection. Associations with advanced-stage disease were estimated in logistic regression models. RESULTS: Patients with low, medium and high SEP had a similar interval from patient-reported symptom onset to diagnosis of 10 weeks. Although this interval varied according to primary symptom and anatomical subsite, no apparent socioeconomic differences were observed within these subgroups. Aligned with the patient-reported symptom onset, a distinct increase in consultation rates was observed at 9 weeks (95% CI [7.3; 10.7]) for patients with low SEP and 7 weeks (95% CI [4.8; 9.2]) for patients with high SEP, with overlapping CIs. Patients with low compared to high SEP had increased odds for advanced-stage glottic and oral cavity squamous cell carcinoma. For the remaining subsites the association varied according to SEP-indicator and TNM-edition. CONCLUSION: The interval from symptom onset to diagnosis and consultation patterns were similar across SEP groups. Still, socioeconomic differences in stage at diagnosis were observed for some - but not all - subsites.

Consistency in contouring of organs at risk by artificial intelligence vs oncologists in head and neck cancer patients.

BACKGROUND: In the Danish Head and Neck Cancer Group (DAHANCA) 35 trial, patients are selected for proton treatment based on simulated reductions of Normal Tissue Complication Probability (NTCP) for proton compared to photon treatment at the referring departments. After inclusion in the trial, immobilization, scanning, contouring and planning are repeated at the national proton centre. The new contours could result in reduced expected NTCP gain of the proton plan, resulting in a loss of validity in the selection process. The present study evaluates if contour consistency can be improved by having access to AI (Artificial Intelligence) based contours. MATERIALS AND METHODS: The 63 patients in the DAHANCA 35 pilot trial had a CT from the local DAHANCA centre and one from the proton centre. A nationally validated convolutional neural network, based on nnU-Net, was used to contour OARs on both scans for each patient. Using deformable image registration, local AI and oncologist contours were transferred to the proton centre scans for comparison. Consistency was calculated with the Dice Similarity Coefficient (DSC) and Mean Surface Distance (MSD), comparing contours from AI to AI and oncologist to oncologist, respectively. Two NTCP models were applied to calculate NTCP for xerostomia and dysphagia. RESULTS: The AI contours showed significantly better consistency than the contours by oncologists. The median and interquartile range of DSC was 0.85 [0.78 - 0.90] and 0.68 [0.51 - 0.80] for AI and oncologist contours, respectively. The median and interquartile range of MSD was 0.9 mm [0.7 - 1.1] mm and 1.9 mm [1.5 - 2.6] mm for AI and oncologist contours, respectively. There was no significant difference in ΔNTCP. CONCLUSIONS: The study showed that OAR contours made by the AI algorithm were more consistent than those made by oncologists. No significant impact on the ΔNTCP calculations could be discerned.

Accelerated loss of lean body mass in head and neck cancer patients during cisplatin-based chemoradiation.

BACKGROUND: This study investigated changes in body weight, lean body mass (LBM), fat mass (FM), muscle strength and functional performance during radiation treatment in head and neck cancer (HNSCC) patients. Secondly, it investigated the impact of cisplatin-based chemoradiation (CCRT) on LBM loss compared with radiation alone. METHODS: 48 patients (all tumor sites) received either 6 weeks of radiation alone (n = 16) with 66-68 Gy in 33-34 Fx, 5-6 Fx/week or CCRT, adding weekly cisplatin or carboplatin (n = 32). LBM and FM was evaluated using Dual-energy X-ray Absorptiometry bi-weekly from pre- to two weeks post-treatment. Maximal muscle strength (knee extension, leg - and chest press) and functional performance (stair climb, chair rise, and arm curl) were assessed pre- and post-treatment. RESULTS: Body weight and LBM had declined significantly already week 2 into treatment and declined significantly further through week 4 and 6 before leveling off after week 6. Bi-weekly, from treatment start to week 2, 2-4, and 4-6, LBM declined 1.2 ± 0.4 kg (p = .002; 95% CI: 0.4;2.0), 2.0 ± 0.4 kg (p < .0001; 1.2;2.8) and 1.4 ± 0.4 kg (p = .001; 0.6;2.2). With a two-week delay, FM declined significantly from week 2-8. All measures of muscle strength declined significantly from pre- to post-treatment. Functional performance was unchanged. LBM loss from pre- to post-treatment was significantly associated with impaired muscle strength (R2 = 0.3-0.5). CCRT patients lost 3.1 ± 0.8 kg of LBM (p = .0001; 1.5;4.7) more from pre- to post-treatment compared with patients receiving radiation alone. Analyses adjusting for nimorazole, tumor stage, baseline BMI, mean radiation dose to constrictor muscles and oral cavity confirmed this. CONCLUSION: Accelerated and substantial LBM loss was already initiated within the first two weeks of treatment - before the onset of radiation-induced mucositis. LBM loss was associated with muscle strength impairment. Patients receiving CCRT experienced significantly larger LBM loss than patients receiving radiation alone. Registered on clinincaltrials.gov (Identifier: NCT05890859).

Missed cancer in the Danish head and neck cancer fast-track program: results from a tertiary cancer center.

BACKGROUND: The Danish head and neck cancer fast-track program is a national standardized pathway aiming to reduce waiting time and improve survival for patients suspected of cancer in the head and neck (HNC). Until now, the frequency of missed cancer in the fast-track program has not been addressed. A missed cancer leads to treatment delay and may cause disease progression and worsening of prognosis. The study objective was to estimate the frequency of patients with missed cancers in the Danish HNC fast-track program and to evaluate the accuracy of the program. MATERIALS AND METHODS: Patients who were rejected from the HNC fast-track program because cancer was not found between 1 July 2012 and 31 December 2018 at Odense University Hospital, Denmark were included and followed for three years. Patients were categorized into groups depending on the diagnostic evaluation. Group 1 included patients evaluated with standard clinical work-up without imaging and biopsy. Group 2 included patients evaluated with imaging and/or biopsy in addition to the standard clinical work-up. The local cancer database and electronic patient records were reviewed to determine if a missed cancer had occurred within the follow-up period. RESULTS: A total of 8345 HNC fast-track courses were initiated during the study period. 1499 were patients suspected of recurrent cancer and were excluded leaving 6846 patients to be assessed for eligibility. Of these, 3752 patients were rejected because cancer was not found. Ten patients were subsequently diagnosed with cancer within the follow-up period resulting in an overall frequency of 0.15%. For group 1 and 2, the frequency was 0.04% and 0.10%, respectively. The sensitivity of the fast-track program was 99.67% and the negative predictive value was 99.73%. CONCLUSION: The frequency of missed cancer in a tertiary HNC center following the Danish fast track program is low.

The influence of tumor volume on the risk of distant metastases in head and neck squamous cell carcinomas.

BACKGROUND AND PURPOSE: Distant metastases (DM) in head and neck squamous cell carcinomas (HNSCC) are in most circumstances non-curable. The TNM staging system is insufficient to predict the risk of DM. This study investigates if the DM risk can be predicted using a multivariate model including pre-treatment total tumor volume for both p16-positive oropharyngeal squamous cell carcinoma (OPSCC) and all other sites (other HNSCC). MATERIALS AND METHODS: The study includes patients with localized pharyngeal and laryngeal squamous cell carcinomas treated with primary radiotherapy from 2008-2017 from three head and neck cancer centers. Patients were identified in the Danish Head and Neck Cancer (DAHANCA) database. Total (nodal and primary) tumor volume (Gross Tumor Volume, GTV) was extracted from local treatment planning systems. The GTV was grouped by volume (cm3) in four intervals and included in a multivariate Cox proportional hazard regression controlled for pre-selected clinical values incl. stage. RESULTS: The study includes 2,865 patients, of which 321 (11 %) had DM post-treatment. The risk of DM was assessed in a multivariate model based on 2,751 patients (p16-positive OPSCC: 1,032; and other HNSCC: 1,719). There was a significant association between GTV and the risk of DM, and in tumor volumes ≥ 50 cm3 hazard ratios of 7.6 (2.5-23.4) for p16-positive OPSCC and 4.1 (2.3-7.2) in other HNSCC were observed. CONCLUSION: Tumor volume is an independent risk factor for DM. The addition of total tumor volume to a predictive model is important to identify subgroups of HNSCC patients at high risk of DM.

Epidemiology, outcomes, and prognostic factors in submandibular gland carcinomas: a national DAHANCA study.

PURPOSE: The aim of this study is to present incidence, histological subtypes, survival rates, and prognostic factors based on a national cohort of patients with salivary gland carcinoma. METHODS: All Danish patients with submandibular gland carcinoma diagnosed from 1990 to 2015 (n = 206) were included and analyzed following histological re-evaluation. Data were collected by the Danish Head and Neck Cancer Group (DAHANCA). Overall, disease-specific and recurrence-free survival were evaluated. Prognostic factors were analyzed with multivariate Cox Hazard Regression. RESULTS: The study population consisted of 109 (53%) men and 97 (47%) women, median age 62 years (range 11-102). Adenoid cystic carcinoma was the most frequent subtype (50%). Tumour classification T1/T2 (75%) and N0 (78%) was most frequent. The mean crude incidence was 0.17/100,000/year. Most patients (n = 194, 94%) were treated with primary surgery, and 130 (67%) received postoperative radiotherapy. The 5- and 10-year survival rates were for overall survival 64% and 41%, disease-specific survival 74% and 61%, and recurrence-free survival 70% and 56%, respectively. Survival rates were higher for adenoid cystic carcinoma compared to other subtypes, but the difference was not significant in multivariate analysis. Recurrence occurred in 69 patients, and 37 (53.6%) of them had recurrence in a distant site. Advanced T-classification and regional lymph-node metastases had significant negative impact on survival rates. CONCLUSION: The incidence of submandibular gland carcinoma in Denmark was 0.17/100,000/year and stable during the time period. The most frequent subtype was adenoid cystic carcinoma. Half of the recurrences presented in a distant site, and multivariate analysis confirmed that advanced stage was independent negative prognostic factor for recurrence and survival.

Association of Smoking, Comorbidity, Clinical Stage, and Treatment Intent With Socioeconomic Differences in Survival After Oropharyngeal Squamous Cell Carcinoma in Denmark.

Importance: The socioeconomic gap in survival after cancer is pronounced among patients with head and neck cancer. Understanding the mechanisms of this gap is crucial to target intervention strategies. Objective: To investigate socioeconomic differences in survival after oropharyngeal squamous cell carcinoma (OPSCC) according to human papillomavirus (HPV) status and the extent to which smoking, comorbidity, clinical stage, and treatment intent explain the survival gap. Design, Setting, and Participants: This nationwide, population-based cohort study was based on prospectively collected information on all patients with a diagnosis of OPSCC from the Danish Head and Neck Cancer Group database and administrative registries. The study included 4600 patients born in 1921 or later, aged 30 years or older, and residing in Denmark 1 year prior to OPSCC diagnosis. Patients with missing information (547 [12%]) were excluded. Patients were diagnosed between January 1, 2008, and December 31, 2019, and followed up until December 31, 2021. Data were analyzed from June 6 to October 4, 2022. Exposure: Socioeconomic position (educational level, disposable income, or cohabiting status). Main Outcomes and Measures: Socioeconomic differences in 5-year overall survival were estimated in Cox proportional hazards regression models by HPV status. The indirect effect and proportion mediated by smoking, comorbidity, clinical stage, and treatment intent were estimated based on a counterfactual approach. Results: The analyzed cohort comprised 4053 patients (1045 women [26%] and 3008 men [74%]). The median age was 61 years (IQR, 55-68 years), and 2563 patients (63%) had HPV-positive OPSCC while 1490 patients (37%) had HPV-negative OPSCC. The 5-year standardized overall survival was 10% to 15% lower among patients with a lower educational level, with low disposable income, or who were living alone (patients with HPV-positive OPSCC, 68%-71%; patients with HPV-negative OPSCC, 31%-34%) than patients with a higher educational level, high disposable income, or a cohabiting partner (patients with HPV-positive OPSCC, 81%-86%; patients with HPV-negative OPSCC, 43%-46%). Among patients with HPV-positive OPSCC, a considerable part of this survival gap was estimated to be associated with differences in smoking (27%-48%), comorbidity (10%-19%), clinical stage (8%-19%), and treatment intent (16%-28%). Among those with HPV-negative OPSCC, comorbidity (12%-22%) and treatment intent (16%-42%) were the primary potential mediators. Conclusions and Relevance: This cohort study suggests that, regardless of HPV status, patients with low socioeconomic position had 10% to 15% lower 5-year overall survival than patients with high socioeconomic position. A substantial part of this survival gap was associated with differences in smoking, comorbidity, clinical stage, or treatment intent at diagnosis.

Larynx cancer survival model developed through open-source federated learning.

INTRODUCTION: Federated learning has the potential to perfrom analysis on decentralised data; however, there are some obstacles to survival analyses as there is a risk of data leakage. This study demonstrates how to perform a stratified Cox regression survival analysis specifically designed to avoid data leakage using federated learning on larynx cancer patients from centres in three different countries. METHODS: Data were obtained from 1821 larynx cancer patients treated with radiotherapy in three centres. Tumour volume was available for all 786 of the included patients. Parameter selection among eleven clinical and radiotherapy parameters were performed using best subset selection and cross-validation through the federated learning system, AusCAT. After parameter selection, ß regression coefficients were estimated using bootstrap. Calibration plots were generated at 2 and 5-years survival, and inner and outer risk groups' Kaplan-Meier curves were compared to the Cox model prediction. RESULTS: The best performing Cox model included log(GTV), performance status, age, smoking, haemoglobin and N-classification; however, the simplest model with similar statistical prediction power included log(GTV) and performance status only. The Harrell C-indices for the simplest model were for Odense, Christie and Liverpool 0.75[0.71-0.78], 0.65[0.59-0.71], and 0.69[0.59-0.77], respectively. The values are slightly higher for the full model with C-index 0.77[0.74-0.80], 0.67[0.62-0.73] and 0.71[0.61-0.80], respectively. Smoking during treatment has the same hazard as a ten-years older nonsmoking patient. CONCLUSION: Without any patient-specific data leaving the hospitals, a stratified Cox regression model based on data from centres in three countries was developed without data leakage risks. The overall survival model is primarily driven by tumour volume and performance status.

Delineation uncertainties of tumour volumes on MRI of head and neck cancer patients.

Background: During the last decade, radiotherapy using MR Linac has gone from research to clinical implementation for different cancer locations. For head and neck cancer (HNC), target delineation based only on MR images is not yet standard, and the utilisation of MRI instead of PET/CT in radiotherapy planning is not well established. We aimed to analyse the inter-observer variation (IOV) in delineating GTV (gross tumour volume) on MR images only for patients with HNC. Material/methods: 32 HNC patients from two independent departments were included. Four clinical oncologists from Denmark and four radiation oncologists from Australia had independently contoured primary tumour GTVs (GTV-T) and nodal GTVs (GTV-N) on T2-weighted MR images obtained at the time of treatment planning. Observers were provided with sets of images, delineation guidelines and patient synopsis. Simultaneous truth and performance level estimation (STAPLE) reference volumes were generated for each structure using all observer contours. The IOV was assessed using the DICE Similarity Coefficient (DSC) and mean absolute surface distance (MASD). Results: 32 GTV-Ts and 68 GTV-Ns were contoured per observer. The median MASD for GTV-Ts and GTV-Ns across all patients was 0.17 cm (range 0.08-0.39 cm) and 0.07 cm (range 0.04-0.33 cm), respectively. Median DSC relative to a STAPLE volume for GTV-Ts and GTV-Ns across all patients were 0.73 and 0.76, respectively. A significant correlation was seen between median DSCs and median volumes of GTV-Ts (Spearman correlation coefficient 0.76, p < 0.001) and of GTV-Ns (Spearman correlation coefficient 0.55, p < 0.001). Conclusion: Contouring GTVs in patients with HNC on MRI showed that the median IOV for GTV-T and GTV-N was below 2 mm, based on observes from two separate radiation departments. However, there are still specific regions in tumours that are difficult to resolve as either malignant tissue or oedema that potentially could be improved by further training in MR-only delineation.

Co-registration of radiotherapy planning and recurrence scans with different imaging modalities in head and neck cancer.

MRI (magnetic resonance imaging) scans are frequently used in follow-up after radiotherapy for head and neck cancer. With the overall aim of enabling MRI-based pattern of failure analysis, this study evaluated the accuracy of recurrence MRI (rMRI) deformable co-registration with planning CT (computed tomography)-scans (pCT). Uncertainty of anatomical changes between pCT and rMRI was assessed by similarity metric analyses of co-registered image structures from 19 patients. Average mean distance to agreement and Dice similarity coefficient performed adequately. Our findings provide proof of concept for reliable co-registration of pCT and rMRI months to years apart for MRI-based pattern of failure analysis.

Open-source distributed learning validation for a larynx cancer survival model following radiotherapy.

INTRODUCTION: Prediction models are useful to design personalised treatment. However, safe and effective implementation relies on external validation. Retrospective data are available in many institutions, but sharing between institutions can be challenging due to patient data sensitivity and governance or legal barriers. This study validates a larynx cancer survival model performed using distributed learning without any sensitive data leaving the institution. METHODS: Open-source distributed learning software based on a stratified Cox proportional hazard model was developed and used to validate the Egelmeer et al. MAASTRO survival model across two hospitals in two countries. The validation optimised a single scaling parameter multiplied by the original predicted prognostic index. All analyses and figures were based on the distributed system, ensuring no information leakage from the individual centres. All applied software is provided as freeware to facilitate distributed learning in other institutions. RESULTS: 1745 patients received radiotherapy for larynx cancer in the two centres from Jan 2005 to Dec 2018. Limiting to a maximum of one missing value in the parameters of the survival model reduced the cohort to 1095 patients. The Harrell C-index was 0.74 (CI95%, 0.71-0.76) and 0.70 (0.66-0.75) for the two centres. However, the model needed a scaling update. In addition, it was found that survival predictions of patients undergoing hypofractionation were less precise. CONCLUSION: Open-source distributed learning software was able to validate, and suggest a minor update to the original survival model without central access to patient sensitive information. Even without the update, the original MAASTRO survival model of Egelmeer et al. performed reasonably well, providing similar results in this validation as in its original validation.